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Small Change, and Other Physics Fun
fishy jew writes "Ever want an easy way to make your 'small change' even smaller? Well, Bert Hickman has it - mix a home-brewed machine, 6.5 kiloJoules, and 100,000 Amps of current! On his website, he has descriptions and pictures of his many exploits with large quantities of electricity, notably including shrinking coins, building a Tesla coil, creating Lichtenberg figures (chaotic sculpture), and more! He has extensively outlined the equipment, procedure, and results for each of his experiments, and included many pretty pictures, too. Here are Google caches for when the site gets /.'ed: Main Page, Shrinking Coins, Tesla Coil, and Lichtenberg Figures."
There is a cool Popular Science article for more information.
Now go buy some coins to fund Bert's efforts!
Remember... ZG9uJ3QgZm9yZ2V0IHRvIGRyaW5rIHlvdXIgb3ZhbHRpbmU=
for the love of god put in a working link
I used to have a cool sig, back when I cared
To see check out auctions by him:
Here, Here, Here, And Here
See Sam Barros' Powerlabs for similar stuff - the guy has got a lot of very cool and realy interesting stuff.
Especially interesting are his high-voltage stuff.
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* Theory of Operation
* Results
* EM Field Theory and Wire Fragmentation?
* Isn't Defacing Money a Federal Crime?
* So Who Invented this Crazy Device?
* References
Theory of Operation:
The Quarter Shrinker uses a technique called high velocity electromagnetic metal forming, or "Magneforming". This technique was originally developed by the aerospace industry in conjunction with NASA, and has been popularized by Aerovox, Grumman, and Maxwell. It involves quickly discharging a high energy capacitor bank through a work coil to generate a very powerful and rapidly changing magnetic field which then "forms" the metal to be fabricated. While it works best with metals of relatively high electrical conductivity such as copper or aluminum alloys, it will work to a more limited extent with poorer conductors such as sheet steel.
In my current system, I charge up a large capacitor bank consisting of a number of large capacitors, each weighing about 165 pounds and about 30" high x 14" wide x 8" thick. A High Voltage relay is used to connect the caps either to a high voltage DC charging supply, or to a high power bleeder resistor chain. A 15 kV 60 mA transformer and a set of 40 kV rectifiers provide the DC charging voltage for the capacitor bank. The primary of the transformer can be overdriven to 140 volts via a variable autotransformer to speed up the charging process. The electrical energy stored in the capacitor bank is proportional to the square of the bank voltage, and the degree of "shrinking" force is directly proportional to the capacitor bank's energy.
The charged capacitor bank is quickly discharged through a single layer work coil made of heavy magnet wire. The coin is held firmly in the center of the coil by a pair of dowel rods so that it's axis of rotation is parallel to the centerline of the coil. This constrains the coin from twisting, and also helps balance the forces wanting to eject it from inside the coil. The two ends of the coil are stripped of insulation and firmly bolted to heavy copper bus bars. The high voltage "switch" that connects the capacitor bank to the work coil is actually a high power triggerable spark gap, called a "trigatron". The main gap electrodes are solid brass, 2.5" in diameter. One of the electrodes is drilled and tapped to hold the triggering electrode (actually a modified spark plug). A triggered spark gap is the only affordable device that can hold off the high voltage and then reliably and efficiently switch the high currents involved in the shrinking process (70,000 to over 100,000 amperes).
The trigatron is fired by applying a high voltage (~40 kV) pulse to the trigger electrode, which then causes the main gap in the trigatron to ionize and fire. Once the main gap fires, current rapidly climbs in the work coil, the rate of change (di/dt) being of the order of 4-5 billion amperes/second. The natural resonant frequency of the LC circuit formed by the capacitor bank and work coil is of the order of 8-12 kHz. Through transformer action, a huge circulating current is induced in the coin, but because of skin effect, this current is confined to the outermost rim of the coin, typically penetrating to a depth of less than 0.050". In clad coins more of this circulating current flows through the better conducting copper center of the clad sandwich than in the outer layers. The coin and work coil magnetic fields oppose each other (Lenz's Law), resulting in tremendous repulsion forces between the work coil and the rim of the coin. The circulating current in the rim of the coin actually prevents the rapidly increasing magnetic field of the work coil from penetrating the interior of the coin.
The large current that's induced into the outer rim of the coin can reach a million amperes or more! The initial bank energy is typically in the range of 3,500 - 8,500 Joules (or watt-seconds) but it is being discharged in microseconds. As a result, the instantaneous power is quite large, and for a brief instant is roughly
Check out the picture and prices of the some of his work on ebay
Try slashdoting that!
Check out these two posts on the topic of /.'ing small sites and why /. can't mirror sites, you may find them informative.
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What happens is the coin ends up _thicker_ than before. Because it is thicker, the coin in turn becomes smaller. The mass is indeed the same before and after.
There is no exotic atomic manipulation going on. Not that people have tried (aka alchemy).
Here are his ebay auctions
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
Better than a mirror: The Wayback Machine!
Try looking here.
Or here.
The archives are kind of old (pre 2004) but they seem to have some of the information.
Huh?
Judging by the description above (yeah it can be wrong, but the site is down for the moment) this sounds a lot like the capacitor bank in the lab I work in. Unlike a tesla coil, this think puts out some serious current. The one we have will output around 120,000 amps at 5 kV. It won't be that much if say a human were in between the connections, but that would be enough to give 250 mA of current to anything with less than 20 kOhm resistance. This sounds very similar to the setup this guy has, so I imagine it can be very dangerous. The lab seems somewhat lax about some of it, but that is because a huge amount of the wiring is well enclosed, which tends to be the exact opposite of all of my home projects.
Even then you have to be careful around pulses of this much current, since often weird things happen with ground. The grounded vacuum chamber we fire this stuff into will often get potentials of several hundred volts across different parts of the same metal chamber. Or if you have something connected to ground in two ways, you can induce a current going from one ground to the other. So it is a matter of knowing what not to touch with your hands or certain equipment when the thing fires.
Here is a link to a site on Tesla Coils, since so many of you seem to be interested in them.
http://www.eskimo.com/~billb/
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It is true that you won't get a lethal shock directly from the high voltage side of a Tesla coil.
One thing you have to watch is the shielding on the 'low' voltage side of homemade equipment. You're going to have components running off 120 V or 240 V line current. If the high voltage side arcs to a low voltage component, suddenly you've got a conducting path through the air (technically, a plasma) attached to potentially several amps of line current. It is possible to deliver a a deadly current this way.
Aside--an arc back to the line can wreak all manner of havoc on other electrical equipment on the same circuit. Your computer won't like it, that's for sure. Please, have properly grounded metal shielding around all line conductors in your experimental area!
~Idarubicin
Regarding the resistance of the human body (to calculate lethal voltages), I remember being told in several HV-safety courses in physics classes that the human cross-body resistance (index finger to index finger) is generally 100 kohms to 1 mohm, depending mostly on the level of sweat on the body, and thus on environmental conditions like heat and humidity. That doesn't mean that 5 kV isn't dangerous, though: remember the 1/10/100 rule: you can feel 1 mA, can't let go at 10 mA due to involuntary local muscle contraction, and at 100 mA you are presenting a serious danger to your heart. Thus, with your 5 kV supply, you'll probably find yourself unable to let go of the power supply's terminals should you touch them. Even the voltages in your house are dangerous, in the right situation (the bathtub scenario: drop a 110v appliance into your bathtub, with you providing a path to ground, and it might not take too much to cause unconciousness and drown you). It's all a matter of knowing what you can do safely.
That's it. I'm no longer part of Team Sanity.